RF Gain 6400

Your two attachments show correct operation on the two RF gain examples; primary focus is on the front end analog to digital conversion.

Your band is very quiet on 20M and only 1 station is visible above (-104dbm) the threshold (-111dbm).

The second example has added 40dbm of gain moving the threshold down to approximately -150dbm, with the panadapter showing a background noise of around -142dbm. If you want to hear all the noise then an antenna gain of around +24 would be suitable. Also observed is the signal shown on the first example is still there AND still the exact same strength (-104dbm) with just the visible threshold lowered exposing the other signals.

Flex staff have discussed the available dynamic range of the A2D converter and recommend, in environments with very high power stations, to keep the RF gain down. Your environment is very quiet so, to see and hear all the noise, you need some front end RF gain.

As you raise the gain you expose more signals until reaching around +24dbm gain, where any more gain only reduces your available dynamic range with no benefits. So use +24dbm gain to hear everything, especially noise, or +16 to hear the stations with no/greatly reduced background noise (comfortable listening).